The proposed research seeks to illuminate the mechanisms of human learning and memory and, in particular, the role of brain oscillations in this vital human capacity. While it has long been known that brain oscillations, and especially the so-called "theta rhythm" (4-12 Hz), are important in rodents as they learn spatial information, the roles of these brain oscillations in human learning and memory have not been adequately explored. It has recently been shown that theta oscillations are readily observed in the human brain, and that they become stronger when a learning task is made more difficult. This finding allows a wide range of new questions to be asked. The proposed research aims to assess whether theta oscillations, as well as higher-frequency gamma oscillations, are causally involved in human learning and memory. More specifically, this research aims to assess theta's role in both human spatial cognition and the encoding, rehearsal, and retrieval processes of working memory. It also seeks to determine the conditions under which task-related cognitive operations produce reset of theta oscillations and whether the "subsequent memory effect" is a consequence of theta reset. Brain waves will be recorded while epileptic patients are undergoing surgical/invasive monitoring as part of the clinical treatment of medically refractory epilepsy. Performed with the highest standard of care, this procedure is potentially curative for the patients and presents an opportunity for collecting data that could lead to new treatments for others faced with neurological disease. By performing cognitive tasks that pose no health risks whatsoever, these patients may provide exquisite data on the involvement of brain waves in cognitive function. The proposed studies will examine the relation between brain waves and both short-term and long-term memory for spatial as well as symbolic/verbal information. Of special interest is whether theta and/or gamma oscillations predict successful recall. These results will inform our understanding of both normal and impaired memory and may ultimately lead to new treatments for debilitating memory disorders.